Travis' Wiki - projects

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tjhowse@undisclosed.example.com (tjhowse) — Wed, 21 May 2025 01:15:39 +0000

Card sorting machine

Android: Netrunner

My eldest son and I occasionally play a game called Android Netrunner together. It's a 1v1 competitive card game where each player assembles a deck of about 50 cards from a pool of a few hundred. It went out of print a few years ago but then a community group took over designing and making new cards. It's similar to Magic: The Gathering in some ways, but without the scummy expensive blind card pack collectathon. You buy a Netrunner set and you get all the cards.

The game has two main factions, Runner and Corporate. When building a deck you choose cards from your faction. There are rules that define what cards a valid deck can contain, and different deck compositions have different strengths and weaknesses. My eldest plays the Runner faction, and I play Corporate.

A problem arises when you're always playing against the same person: Each player is trapped in a constant cycle of adaptation to their opponent's deck. Exploiting their weaknesses and mitigating your own. This tends towards a see-saw pattern of wins and losses, and involves a lot of deckbuilding which neither of us particularly enjoy.

Solution (?)

I think it would be fun to build a robot that can do deckbuilding for you. The entire card pool is well-documented with online tools like Jinteki.net, and the rules for deck validity are easy to codify. I think it might be fun to have a computer formulate a random-but-valid deck, and to build a robot to physically pluck those cards out of the pool so you can be ready to play.

Motive force

I've used stepper motors in a few projects, recently my sand drawing robot. A stepper motor is able to turn its shaft like a regular motor, but can also move it in tightly-controlled “steps”. Usually 200 steps per revolution, but “microstepping” can divide a step up into sub-steps. 16 or 32 microsteps-per-step are common, giving angular accuracy in the range of 0.1° to 0.01°. You can make a normal motor turn by applying the appropriate voltage. In contrast stepper motors require carefully sequenced pulses to turn.

I've been looking for an excuse to play with closed-loop stepper motors. These have the stepper control circuitry built-in, and a sensor to measure the angle of the shaft. You provide the motor a DC voltage and step/direction signals to make them turn. They also have a serial UART interface, which means you can send them commands from a microcontroller rather than counting out hundreds of step pulses.

Matthias Wandel has an excellent video on them:

I settled on a MKS Servo42C because they are cheap, readily-available and have a UART interface.

Diversion into interfacing

I was shocked to learn there was no batteries-included python library for controlling these steppers, so I wrote one and published it on pypi. Now you can control your stepper with code like

from time import sleep
from servo42cUart import Servo42CUart

s = Servo42CUart("/dev/ttyUSB0", 9600)

# Start turning clockwise at full speed
s.set_constant_speed(Servo42CUart.Direction.CLOCKWISE, 127)

# Wait a second
sleep(1)

# Stop turning
s.stop();

# Turn 360 degrees, assuming 16x microstepping, as fast as possible.
s.set_angle(Servo42CUart.Direction.CLOCKWISE, 127, 200 * 16)

Eyes

The robot will need to be able to identify a card for it to be sorted. I plan to do this with a webcam and tesseract-ocr. This is a very powerful text recognition engine that Google publishes open-source. Some early testing has yielded promising results. I set up a HD webcam with a goose-neck worklight, with a white background. The webcam is connected to an old Raspberry Pi Model 3, running Debian 10.

Other similar projects have used more complex machine learning smarts to identify the whole card, graphics and all, rather than just looking at the text. I'm going to see how far the text-only approach takes me, so I can keep all the brains on a single old RPI.

A cobbled-together test rig.

The view through the webcam.

tesseract-ocr read:

NOISE

IDENTITY: G-mod

Whenever you install a virus program,
the Corp trashes the top card of
R&D.

“Watch this. It'll be funny,”

Which is pretty impressive for such a bodge-fest.

The view through the webcam.

Result:

INFILTRATION
Gain 29 or expose | card
Bring back any memories, Monica?’
John “Animal” McEvoy
0 2012 oats le Coast LLG, @2012FFG

Next steps

Next up I have some mechanical design work to do. The machine must:

Support a stack of cards,
Provide outlets through which cards can be fed,
A means of transmitting the motor torque into card-sliding action,
Supporting lighting,
Supporting the camera.

Should be fun! I'm anticipating some challenges:

Handling sleeved and unsleeved cards,
Glare from the lighting,
Camera focus/exposure issues,
Ensuring single-card feeding at different stack heights,
Keeping the camera view unobstructed by mechanical gubbins,
Fuzzy-matching card text against the card database.

9_wivenhoe

tjhowse@undisclosed.example.com (tjhowse) — Tue, 11 Feb 2025 07:26:39 +0000

Winter (??) Sailing

It's starting to get a bit cooler here in Brisbane. By which I mean it gets below 20°C at night. Spare us your scorn, we know we deserve it.

2024-05-06 The river

Another trip out onto the Brisbane river from the Colmslie recreation reserve. Not much to report on this one. We had a bit of trouble launching due to dock congestion, but we got out and had a good time. I lectured the kids on the loathsome game of golf and its barren monocultured hellscapes. We had a play around with the boom vang on our downwind run back. Kept the boom much more well-behaved. Lost my sunnies into the river when I was dropping the sails. RIP.

2024-05-19 Wivenhoe Dam

The stars finally aligned! We had a free Sunday coming up and a 8-10 knot forecast. We had a few things to check first. I picked up a new handful of cheap sunnies from the safety shop, and I tightened the loops holding the luff of the jib stretched along its leading edge wire. Hopefully this should keep it happier.

I replaced the rivets holding the tiller onto the arm joining both the rudders, they were getting a bit loosey-goosey.

I showed Sam how to deploy our tiny little anchor. If it looks woefully inadequate: that might be reasonable.

I got the boat all packed up and ready to go on the night before, using a new checklist I put together:

☐ Radio
☐ Bungs
☐ Charts
☐ Water
☐ Food
☐ Sunscreen
☐ Life jackets
☐ Anchor
☐ Sails
☐ Reef shoes
☐ Leatherman
☐ Sail tape
☐ Tape
☐ String
☐ Multigrips
☐ Spare rope
☐ Trailer tires pumped
☐ Gopro
☐ Key floats
☐ Tell someone where we’re going and when we’re getting back

Getting up at 08:00 on a Sunday, early by our standards, demands a pot of porridge to bribe everyone out of bed. I may have overdone the cinnamon.

The traditional sailing lunch bag.

Mostly packed and ready to roll.

Wivenhoe is about 1.5 hours' drive from our place. I threw an extra ratchet strap around the top of the boat to hold it down to the trailer. This marginally reduced boat-flying-off-trailer anxiety. We decided to put in at the Hays Landing boat ramp.

The drive was uneventful. We listened to a few episodes of Sawbones to keep the kids sane. We got a few spectacular peeks of the lake and the dam itself on the way in. The Hays Landing boat ramp was closed when we got there, so we diverted slightly to the nearby Billie's Bay ramp. By the time we got there the extra strap I put around the boat had worked its way loose and was flopping uselessly. Erk.

Alex and Sam doing pre-launch checks.

The sky was a perfect blue gradient while we rigged up, without the slightest breath of wind. C'mon BoM, don't fail me now. I was given hope by another sailor turning up at about the same time as us. He had an eastern European accent. Czech? Bulgarian? Ukrainian? We had a chat with him about his boat. He had a kind of turbo-kayak, with a sail, retractable outriggers, oars, and a sweet pedal-driven flippy-flappy underwater paddle mechanism. Very cool.

Just as we launched the wind started to pick up enough for us to get underway. Phew.

Our loose goal was to explore around the dam and find interesting stuff. There was plenty of wildlife about, including pelicans and herons/egrets. The kids had been nagging us for ages to let them go for a swim off the boat. We didn't really want to do that in the Brisbane river, as it is pretty scummy. We took advantage of a lull in the wind by throwing in our brand new anchor, followed by the kids.

We tied a rope around Sam's life jacket, just in case.

Both kids pretty quickly soured on swimming around the boat, possibly due to the extremely reasonable Deep Sea Willies combined with the cold (for us) temperatures. Just after we got them back onboard the wind picked up and we immediately started dragging anchor as if it wasn't there. Lesson learned: Get a bigger anchor, or drop sails at anchor.

We pulled up on a clear patch of shore on the far side, about 2.5km straight across from where we started, to have a walk around and stretch our legs. We found a lot of cool rocks. There was a Turdis barely visible on the other side of some scrub. We later learned that slightly further along the shore was a dedicated boating stopping point, with a picnic table, toilets, and a bin. Whoops!

Michelle exploring.

After our stop the wind picked up to around 10-15 knots. We zoomed back across the dam to check out a picnic area just north-west of the boat ramp. Michelle lost her hat, as per tradition, but we recovered it without incident.

The crossing point shows where the hat landed.

Our second stop, at the Hays landing BBQ spot.

Alex and Michelle

I was a little concerned the building wind would carry our boat off the shore, so we had a quick afternoon tea and got back underway quickly. Some people on the shore came to watch us sail off. We were getting some good splashes over the bow and the kids didn't appreciate getting soaked. We decided to head back to the boat ramp, but not before a little extra exploration to see some cows.

Back at the boat ramp.

Sam and me.

And that's about it! The kids were zonked and fell asleep in the car on the way home. Next time we come out here we're going to be more ambitious and head up to an island we can see on the maps, and maybe visit the stopping point around the corner from where we first stopped.

Video

11_river - created

tjhowse@undisclosed.example.com (tjhowse) — Fri, 07 Feb 2025 05:29:11 +0000

Summer 2024-2025

In a gap between two surgeries we rushed out for a quick afternoon sail.

2025-02-01

This was our first outing with the new halyards and the gopro. The forecast was for 10-13 knots. It was gusting to about 18-20 when we got there, with a light drizzle. We got out into the water without too much hassle. Michelle narrowly avoided throwing the car keys into the river. I succeeded in throwing my sunglasses into the river, but managed to retrieve them before they sank.

Michelle recorded a brief snippet of footage while we were underway. I need to build a mount to attach it to the end of the boom.

The boltrope on the foot of the mainsail pulled out of the boom again. The outhaul had come loose again. The new halyards worked great. No worries at all. Unfortunately I forgot to record the track of our journey. Next time, for sure.

10_river - created

tjhowse@undisclosed.example.com (tjhowse) — Mon, 09 Sep 2024 04:03:44 +0000

Spring 2024

Winter's over! Sailing season is here again! We had a brief attack of 35°C weather, then it dropped by 10°C, then it warmed up a bit again.

2024-09-01 Father's day

On Australian father's day I invited my Dad out on the river with the boys and me. This time I decided to take us upriver to check out Newstead. We'd be sailing past HMAS Moreton and a few citycat stops.

For this outing I wanted to try a different way of rigging the jib. Our jib is slightly undersized for the boat, so there's a fair length of halyard, about 300mm, between the head of the sail and the pulley on the mast. This means the head can flop about when we're getting close to tacking, spilling wind. This can make it difficult to maintain momentum through a tack. As an experiment I threaded the forestay through the halyard shackle, and secured the jib tack slightly higher up along the forestay, rather than right at the bottom where it usually sits.

We launched from our usual Colmslie recreation reserve boat ramp and headed upriver. There was a nice 10 knot northerly and patchy cloud cover. There were a few citycats cruising around. Sailing downwind of the big apartment blocks on the north shore was a bit annoying as the wind was pretty squirrelly. We tied off to a floating anchor point marked “NOT FOR PUBLIC USE” just off some fancy riverfront houses in Bulimba and broke out the eski for some apple slices, mint slices and zooper doopers. The wind spun us around the buoy a few times as we ate.

After the break we sailed back downriver to the boat ramp. We had some difficulty in tacking once or twice. My new jib rigging didn't seem to have helped much. Both the halyards are quite stretchy. I think it might be worth replacing them.

overview

tjhowse@undisclosed.example.com (tjhowse) — Sat, 01 Jun 2024 05:03:05 +0000

This project is about creating a functional replica of a Wehrmacht Engima machine from World War 2.

I am to build an electromechanical device that can decode enigma-coded messages. I'm not aiming to reproduce the visuals of the original enigma.

Great reference doc here: http://users.telenet.be/d.rijmenants/en/enigmatech.htm

The original source is gone, I've pushed up a backup here: https://github.com/tjhowse/enigma

Nazis were and are bad, their philosophy was bad, and they did bad things.

Work logs:

work_log_1

Youtube playlist